Ordering of oxygen moments in ferromagnetic edge-sharing ${\mathrm{CuO}}_4$ chains in ${\mathrm{La}}_{14-x}{\mathrm{Ca}}_x{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$

Neutron scattering measurements have been performed on the $S=$$\frac{1}{2}$ quasi-one-dimensional system ${\mathrm{La}}_5{\mathrm{Ca}}_9{\mathrm{Cu}}_{24}{\mathrm{O}}_{41},$ which consists of edge-sharing ${\mathrm{CuO}}_4$ chains. We observed that the chains show an antiferromagnetic long-range ordering below $T_N=10.5\mathrm{K}$ with ferromagnetic correlations within the chain. In the antiferromagnetically ordered phase, an ordering of oxygen moments ($\sim 0.02{\mu }_B)$ as well as that of Cu moments ($\sim 0.2{\mu }_B)$ is observed. The oxygen moments are coupled with Cu moments ferromagnetically.